For years, Laura Teresa Leon Sanchez says, she was beaten, raped and robbed by her boyfriend. If she tried to leave, he threatened to have her deported.

"I was a ghost. I was nothing," said the Mexico City native who was living in the United States illegally. "He would say, 'I'll call immigration, and just like this, you'll be gone.'"

Sanchez eventually got help from authorities _ along with a special visa offered by the government to encourage illegal immigrants to report violent crime.

Created in 2000, the "U" visa program was on hold until rules for its implementation were adopted in 2007. Now the government is approving thousands of requests.

Records from the U.S. Citizenship and Immigration Service show that 4,400 visas were issued this fiscal year _ up from just 52 last year.

The effort is consistent with the new priorities of federal immigration agencies under the Obama administration.

"It's certainly a sea change," said Mary Giovagnoli, director of the Immigration Policy Center in Washington. "The sensitivity toward people who through no fault of their own are in dire straights is enhanced now."

About 13,000 applications are still pending. Half of those are awaiting more information from the applicant, and half are in a backlog that immigration officials are pushing to resolve.

Some immigrants never apply because they fear police or worry that they might end up in deportation proceedings.

"There's nothing worse than knowing someone is exposed to violence, and to hear them say they don't want to live with that violence, but they're too afraid to speak out," said Nancy O'Malley, district attorney for Alameda County, which includes much of San Francisco Bay.

"We've seen too many immigrant women who have either acquiesced or stayed silence because they're afraid to go to the government because of their status."

In January, the immigration agency's ombudsman expressed concern about processing delays. In response, the agency added staff, reorganized the work and picked up the pace.

Immigration officials have also reached out to law enforcement, attorneys and advocates to spread the word about the program.

"This is a vulnerable population," said Chris Rhatigan, a spokeswoman for Citizenship and Immigration Services. "And if they're eligible for this protection, and they've worked with law enforcement, we're doing everything that we can to make sure they get this protection."

Immigrants benefiting from the program include hundreds of women alleging rape, female genital mutilation and sex trafficking. But government records show the overwhelming majority _ upward of 4,000 cases _ are domestic violence victims.

Before a U visa is approved, police, prosecutors or a judge must certify that the applicant has cooperated in arresting or prosecuting the alleged attacker. Immigrants may do so without fearing deportation.

"It's a good thing for the community and a good thing for the police. "We're all on the same side," said Oakland police Lt. Kevin Wiley, commander of special victims unit. He has certified 171 visa applications since November 2007.

But immigration advocates say law enforcement agencies across the country have wide-ranging standards for what constitutes cooperation, meaning the process is easier for some immigrants than others.

"It's very frustrating, the inequity of it," said Kimberly Baker Medina, an immigration attorney in Fort Collins, Colo., who says she has struggled to get applications certified by law enforcement.

Sonia Enriquez Perdomo called Tavares, Fla., police to report her boyfriend had tried to choke her. But it was Perdomo's undocumented sister, not her abusive boyfriend, who was detained.

According to court papers, when police checked the identification of everyone in the house, they learned the victim's sister, Rita Cote, had been brought across the border illegally by her family when she was 15.

Tavares Police Capt. Danny Feleccia said officers followed standard procedure by checking identification and used their own judgment in concluding that the domestic abuse complaint was unreliable.

"The officers did what they were supposed to do," Feleccia said.

The American Civil Liberties Union won Cote's conditional release, and a temporary stay of deportation.

Back in Oakland, fear of deportation kept Sanchez from calling police on her abusive boyfriend until November 2007, when she stumbled out of her house, beaten and barely able to walk.

She came upon police officers and told them everything: The man she met at church four years earlier had hit her with a belt, kicked her and dragged her by the hair. She was bleeding internally.

Her boyfriend was arrested. She took out a restraining order, but he came back to harass her. She continued to work with police.

Her visa now in hand, she is rebuilding her life by cleaning houses and paying for the education of her high-school and college-aged daughters in Mexico City.

The attorney who handled Sanchez' case said getting the visa transforms her clients.

"They go from being hopeless, marginalized, isolated, defeated, to being on the road up, with all the resources that you need," said Susan Bowyer, managing attorney at the International Institute of the East Bay, a nonprofit organization that has submitted more than 500 applications, and gotten 190 approved so far.

Still, the number of visas granted remains several thousand below the 10,000 allowed per year under the law. Immigrant advocates say the program is still plagued by delays _ and thousands of victims are waiting.

Applicants can wait more than a year to hear if they will get a visa, said Julie Dinnerstein, a New York-based immigration attorney who has had 153 cases pending for more than a year.

In the meantime, many applicants find themselves isolated and unable to work.

In Raleigh, N.C., Bertille Boutamba is having a hard time supporting herself and her two American-born children since leaving her abusive husband.

Boutamba, 35, is originally from the west African nation of Gabon. She spoke repeatedly to police and prosecutors, and she's been waiting for her visa request since July 2008. The struggle to provide for her family leaves her dependent on friends from church.

"I feel ashamed each time I'm sitting at the church," Boutamba said through tears. "I can't even look people in the face because of my situation."